1. Field of the Invention
The present invention relates to a temperature control method and a drying device for drying a photosensitive material, which has been processed by processing solutions, by heated drying air.
2. Description of the Related Art
A photosensitive material, such as a photosensitive film, on which imagewise light has been exposed, is subject to processing solutions such as developer, fixer, and washing water. Thereafter, the wet photosensitive material is finished by a drying device. Generally, in the photosensitive material drying device, while the photosensitive material is conveyed by a plurality of rollers disposed within a drying chamber, drying air, which is heated to a predetermined temperature, is blown to the surfaces of the photosensitive material. In order to provide drying air at a predetermined temperature, the temperature of the drying air supplied within the drying chamber is measured, and the temperature of a heater for heating the drying air is controlled so that the photosensitive material is dried in an optimal drying state.
In this way, the drying air is heated to the predetermined temperature by the heater. However, when the photosensitive material is transported through the drying chamber after the drying air is heated to the predetermined temperature, there may be drying irregularities in the photosensitive material. If the rollers, guides and the like disposed in the drying chamber for conveying the photosensitive material have not been heated to substantially the same temperature as the temperature of the drying air even if the drying air within the drying chamber is at the predetermined temperature, there is the concern that there will be drying irregularities in the photosensitive material because the photosensitive material is brought into contact with the relatively cold rollers, guides or the like in the chamber. Time is required for the rollers, guides and the like, which are disposed within the drying chamber and which convey the photosensitive material, to be heated to substantially the predetermined temperature by the drying air. Therefore, before the photosensitive material, which has been subjected to various processes such as developing, fixing, washing, etc. is dried, the heated drying air should be supplied to the interior of the drying chamber for enough time required for heating the rollers and the like to substantially the same temperature as the drying air which is heated to the predetermined temperature, i.e., the drying air is supplied for approximately a predetermined time.
While the photosensitive material is dried, the temperature of the heater is controlled so that the drying air is kept at approximately the predetermined temperature. However, when processing of photosensitive material has not been carried out for a long time, so-called "standby control" is effected in which a heater serving as a heating means is turned on and off at predetermined time intervals so that the temperature of the interior of the drying chamber is kept within a predetermined temperature range lower than the temperature of the drying air when the photosensitive material is dried. In this way, the temperature of the drying air may at any time be switched to the temperature at which drying of the photosensitive material is possible.
However, it is difficult to determine with absolute certainty the time required for heating the parts such as the rollers within the drying chamber to a temperature at which drying of the photosensitive material is possible. This time depends on the temperature surface temperature of the heater, air temperature in the drying chamber, atmospheric temperature, etc. Therefore, the raising time from the time the power source of the heater in the photosensitive material drying device is turned on to the time when drying of the photosensitive material is possible must be set with some leeway. In practice, even if the rollers and the like within the drying chamber have been heated to a temperature at which the photosensitive material can be dried under optimal conditions, we cannot start the operation of the drier or of the automatic developing processor, which is a drawback at times when it is desired to process and dry the exposed photosensitive material rapidly and to have the dried photosensitive material quickly. Further, when a photosensitive material is not being processed, the heater serving as the heating means is turned on and off in a preset cycle. The temperature of the rollers and the like is difficult to control, and the temperature does not fall within the predetermined temperature range.